Just to bring all up to date, I posted this about 10 years ago and it remains useful for those choosing between these two rounds.
The 250 grain bullet now available, for the .300 Weatherby, is by Hawks. I had some loaded by Superior Ammo and am taking them with me to Alaska, on Sunday, to hunt Coastal Black Bear.
The ballistics of the .338 and .300 Weatherby, using a 250 grain bullet are very similar. The only published ballistics for the .300 Weatherby using a 250 grain bullet is that for the Barnes Original. The comparison at MV is .338: 2660 fps and .300 Wby: 2650 and at 100 yards, .338: 2456 and .300 Wby: 2433. Out to 300 yds the comparison is very similar. On the issue of energy, at muzzle, .338: 3927 ft lbs and .300 Wby: 3898 ft lbs and at 100 yds, .338: 3348 ft lbs and .300 Wby: 3256 ft lbs.
While it is true that the .338 has a slightly larger diameter there are other factors consider, ie., sectional density and ballistic coefficient. On sectional density the .338 is .313 and the .300 Wby is much greater at .376. Equally impressive, for the .300 Wby, is the ballistic coefficient. For the .338 it is .291 and for the .300 Wby it is .417.
So, with a 250 grain bullet there are arguments for both. My preference is the .300 Wby which is why I own one. It is incredibly flexible, bullets available from 110 grains to 250 grains, and when equipped with the Pachmayer and with the Accubrake there is practically no recoil.
To take this one step further, when you get to bullets of less than 250 grains the superiority of the .300 Wby is without question. Using a 180 grain Accubond the .338 has a mv of 3100 and the .300 Wby a mv of 3250. At 100 yards the .338 is at 2840 and the .300 Wby at 3051. On energy at the muzzle the .338 is 3842 ft lbs and the .300 Wby at 4223. Then at 100 yds the .338 is 3225 ft lbs and the .300 Weatherby is at 3721 ft lbs. Again, out to 300 yards the comparison is abut the same. Sectional density for the .338 is .225 and for the .300 Wby is .271.
Then there is the issue of flatter trajectory.
In my opinion, the statistics speak for themselves. Roy Weatherby simply outdid the world when he came up with the .300 Weatherby Magnum.
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